The present invention relates to the control of offensive odors. More particularly, the present invention relates to a method of controlling offensive organic and/or amine odors in a gaseous or liquid medium by contacting the medium with a kraft pine lignin.
Objectionable odors in aqueous systems such as industrial aqueous systems can present both aesthetic and health concerns. For example the presence of organic materials particularly organic acids and amines such as organic amines can give rise to objectionable odors. The existence of such objectionable odors can be a problem aesthetically. For example, homes, schools, parks or businesses located near an industrial facility that emits organic acid or organic amine odors will find such odors objectionable. In addition, health issues may arise.
Odor control methods can be chemical or mechanical. Ventilation of indoor air is often employed. If the air is vented without treatment, the odoriferous air is simply diluted by the outside air so that the concentrations of odor causing chemicals are below the detection threshold. Alternatively, exhaust air may be treated with scrubbers, biofilters or absorption units. In scrubbers, the water employed may contain chemicals which increase the efficiency and/or react with the odor causing chemicals. For example, acid gases are often scrubbed with a caustic solution or a combination of caustic and sodium hypochlorite. In biofilters, a solid support is seeded with microbial cultures which degrade the odor causing chemicals. A variety of support and microbes are available for liquid and gaseous streams. Adsorption units typically contain some sort of solid sorbent such as activated carbon or other high surface area material. Other mechanical solutions to odor problems include electrostatic precipitators and combustion.
Many chemical treatments for odor control are masking agents. Masking agents can be applied as solids, liquids, or gases. Most of the essential oils (limonene, pinene etc.) and esters used for odor control may be considered masking agents. Masking agents do not actually react with the odor causing chemical but decrease the perception of the odor by overpowering it. Masking agents replace the objectionable odor with a more pleasing odor. Masking agents may exacerbate problems with odors that are health hazards by decreasing the perception of the odor without decreasing its toxicity. Often, the smell of a masking agent itself can become objectionable.
Odor neutralization is a phenomenon in which odors can seem to cancel each other. Rather than over powering an offensive odor with a more pleasing one of a masking agent, the aim of neutralization is to produce a net zero odor. In the process of neutralization, there is no chemical interaction between the odor causing chemical and the neutralizing agent. Like masking agents, they can exacerbate a problem if the odor that is neutralized is also toxic. Another disadvantage of neutralizing agents is that multi-component odors will typically require a multi-component blend of neutralizing chemicals. To completely neutralize complex odors, individual blends of neutralizing chemicals would need to be developed for each individual application.
Many chemicals can be used to react with offensive odors. For example U.S. Pat. No. 4,551,305 discloses a formulation for reducing organic waste odors which includes a spent sulfite liquor containing lignosulfonate and sugars, acetic acid, phenolic carbonyl and an alkaline pH-modifying substance. The combination is effective at reducing amine and ammonium odors. U.S. Pat. No. 4,902,489 discloses a method for deodorizing offensive gases comprising treatment with a lignin solution after washing the gas to remove basic offensive ingredients.
In general, the present invention relates to removing odor from an aqueous system by adding an effective dosage of a treatment agent to the aqueous system or spraying the treatment agent into the atmosphere near the aqueous system. The problematic odors controlled by the present invention can be a result of organic acids and/or organic amines. The odor control treatment of the present invention comprises an aqueous solution of kraft pine lignin. The kraft pine lignin is preferably anionic and substantially free of sulfonate. The treatment is preferably a salt form such as a sodium salt of anionic kraft pine lignin. By substantially sulfonate free, it is meant that sulfonate substitution of the kraft pine lignin is not intentionally provided. However, trace amounts of sulfonate may exist in the preferred anionic kraft pine lignin.
In accordance with the present invention, it has been found that kraft pine lignin is effective at controlling undesirable odor of aqueous systems which result from the presence of odoriferous organic acids and/or organic amines. The treatment of the present invention can be added directly to the aqueous system, added to components such as scrubbers that contact the aqueous system or sprayed into the atmosphere near the aqueous system. The odor control of the present invention is achieved by any means of bringing the kraft pine lignin into contact with the odoriferous component of the aqueous system.
The present invention involves controlling offensive odors from aqueous systems through the addition of a substantially sulfonate free, anionic kraft pine lignin to the aqueous system or the atmosphere near the aqueous system. Offensive odors such as odors caused by organic acids and/or organic amines can be controlled by the method of the present invention.
Typical organic acids and/or organic amines which can cause objectionable odors when present in aqueous systems include skatole (3-methyl 1-H indole), butyric acid, propionic acid, valeric acid, cadaverine(1,5 pentane diamine), putrescine (1,4 butanediamine), butylamine, propylamine and ammonia. These materials are known to result in objectionable odors in several industrial operations including meat processing, dairy processing, corn milling, paper processing and beet processing.
The treatment of the present invention is a substantially sulfonate free, anionic kraft pine lignin. Preferably the treatment is the sodium salt of substantially sulfonate free, anionic kraft pine lignin having a molecular weight of from about 1000 to 500,000 and most preferably having a molecular weight of about 50,000. The treatment is preferably provided as an aqueous solution of substantially sulfonate free, anionic kraft pine lignin having a concentration of from about 0.1% to about 30% actives. Such an aqueous solution of substantially sulfonate free, anionic kraft pine lignin preferably has a pH of from about 8 to 11. The aqueous treatment solution can be added to an odoriferous aqueous system in a concentration ranging from about 10 ppm to about 500 ppm. An exemplary material is Indulin C available from Westvaco Inc. Indulin C is a kraft pine lignin having a molecular weight of about 50,000 available as a brown powder of moisture content ranging from about 4-5%. Indulin C has a pH of about 10.2 in a 15% w/w aqueous solution.